While a portable lighting apparatus such as a flashlight having a small filament light source is generally constructed with a reflector shaped to produce a narrowly focused spot beam for illumination of a distant object, it is often desired to produce a broader flood beam to illuminate a close-by extended area using the filament light source. U.S. Pat. No. 5,424,927 issued to David R. Schaller et al. Jun. 13, 1996 discloses a flashlight having a parabolic reflector that terminates in a rectangular opening. The parabolic reflector collimates light emitted from a filament positioned at the reflector focal point. A rectangular electro-optic device driven by electronic circuitry covers the rectangular opening and operates in a first state to pass the collimated light to form a spot beam. In order to produce a flood beam, the state of the electro-optic device is switched to refract the collimated beam produced by the parabolic reflector. The use of both an electro-optic device and the required electronic drive circuitry, however, is costly and the electro-optic device reduces the amount of light directed from the reflector.
Reflectors for rectangular openings are known which have a pair of opposing parabolic or elliptic reflecting portions that are joined by planar reflective portions. The reflections from the planar reflective portions, however, often result in a non-uniform flood beam. U.S. Pat. No. 4,386,824 issued to Geoffrey R. Draper Jun. 7, 1983 discloses a motor vehicle rectangular lamp reflector which has parabolic lateral reflective portions and upper and lower reflective portions shaped to provide an infinite number of parabolic or elliptical curves. The parabolic or elliptical curves extend forwardly of the reflector body and terminate at the rectangular front opening thereof. The upper and lower reflective portions have foci (focal points) and focal axes that are coincident and increase progressively in focal length from the center of the reflector to the lateral reflective portions. As a result, a relatively complex arrangement of curves on upper and lower reflective portions is required in order to produce a flood beam. Further, the use of concave parabolic lateral reflectors results in non-uniformities in the produced flood beam.